1. Field of the Invention
The present invention generally relates to an apparatus and method for transmitting and receiving data in a mobile communication system. More particularly, the present invention relates to a data transmission apparatus and method and a corresponding data reception apparatus and method, for improving system performance in a mobile communication system.
2. Description of the Related Art
Generally, mobile communication systems such as Code Division Multiple Access (CDMA) use error correction coding schemes to reduce the effects of signal distortion and noise during high-speed data transmission and reception.
To use an error correction coding scheme, a transmitter avoids burst errors by subjecting adjacent symbols or bits to irregular channel fading using a plurality of interleavers. The transmitter multiplexes interleaved data blocks, maps the multiplexed data blocks to bursts, and performs symbol mapping according to a high-order modulation scheme such as 8-ary Phase Shift Keying (8PSK), 16-ary Quadrature Amplitude Modulation (16QAM), 32QAM, or 64QAM.
Symbol Mapping based on Priority (SMP) was proposed for implementation in the transmitter to improve system performance by symbol mapping based on the priorities of systematic bits (S bits) and Parity bits (P bits) resulting from channel coding according to a coding scheme. In SMP, conventionally, a first interleaver interleaves the S bits and a second interleaver interleaves the P bits. Thereafter, symbols are mapped according to a coding rate and the reliability pattern of a high-order modulation scheme. When the SMP is applied to transmission data blocks, the number of high-reliability bits is determined by the reliability pattern of a used modulation scheme. For example, a reliability pattern can be [H H L L] for 16QAM and [H H M M L L] for 64QAM.
To facilitate application of SMP based on the reliability pattern of a modulation scheme, the S bits and the P bits can be divided into two sub-blocks. In the sub-block division scheme, a distributor efficiently divides a coded bit block (or a coded bit stream block) received from a channel encoder into two sub-blocks and provides them to interleavers, instead of simply transmitting the coded bit block separately as the S bits and the P bits to the interleavers in a system supporting a plurality of coding rates and data rates. The two sub-blocks are independently interleaved, multiplexed, and burst-mapped.
In the transmitter, the distributor divides a channel coded data bit stream including S bits and P bits into two sub-blocks. The first and second interleavers interleave the sub-blocks independently. To overcome burst errors during transmission on a fading channel, the data of these interleaved data blocks should be distributed to a plurality of bursts. Also, it is preferred that the performance of the data of each burst is improved by symbol mapping such as SMP that can be applied to a high-order modulation.
Accordingly, there is a need for an apparatus and method for transmitting and receiving data by symbol mapping based on priorities of S bits and P bits and less sensitive to a channel fading environment, such as SMP, in order to improve system performance.